Surface illuminating devices are well known. For example, light fixtures are used in museums to illustrate paintings and on highways to light up directional signs. In another common use, conventional light fixtures are utilized to illuminate outdoor advertising, found along highways and thoroughfares.
The well-known term “billboard” is often used for poster panels and bulletins. A typical bulletin is utilized to advertise printed or hand painted messages and is usually found in high density traffic locations. The bulletin typically has an area of 672 square feet, having a height of about 14 feet and a width of about 48 feet. Poster panels are smaller, with an area of about 300 square feet, a height of about 12 feet and a width of about 25 feet. A poster panel is typically about 6 feet high and approximately 12 feet wide, having an area of about 72 square feet. While this specification sets forth the present invention as it relates to bulletins, it will be recognized that the present invention has application to a variety of cases wherein it is desirable to illuminate a large flat surface. For convenience, the “billboard” will be used herein in reference to such surfaces.
In a many cases, billboards display graphic advertisements or public service messages and the boards are oriented so as to be seen by motorists and pedestrians passing them during travel. Typically, a billboard having a length of 48 feet is illuminated from below by four light fixtures equidistantly spaced along a bottom surface of the board and separated from the board by about 4 to six feet. An important desirable characteristic of billboard light fixtures is that, when spaced along the lower edge of a billboard, they provide uniform lighting to the board so that no dark spots or shadows occur across the surface thereof. This characteristic is generally not found in conventional billboard light fixtures.
It is not uncommon in a billboard lighting system, utilizing four light fixtures, for the billboard to have four islands of bright illumination with shadowed areas at the periphery of the islands and between the islands of light. The result is an illuminated billboard that is not esthetically attractive and which, in some respects, fails to convey the advertiser's message because of uneven illumination or shadows on the board.
Thus, there is a need for a light fixture, adapted for use in illuminating flat surfaces such as billboards, that can illuminate the surface in a generally uniform manner while substantially reducing shadowed areas.
In view of the environment in which the device is utilized, such a light fixture should have some weather resistant capabilities since it will be exposed to a variety of changing and, sometimes severe, weather conditions. It should be resistant to invasion by insects and other pests and it should be easily maintained and capable of being opened quickly and easily for bulb replacement and maintenance. In addition, the light fixture should have good aerodynamic characteristics so as to withstand high winds without damage.
Further, the fixture should not contribute to “light pollution” by scattering light away from the object being illuminated. Still further, the light fixture should have a low profile so that it would not draw the eye of the observer to itself but, instead, would induce the observer to look at the surface being illuminated.
In some cases, conventional light fixtures fail to satisfy the aforesaid criteria.
In view of the foregoing, there is a need for a light fixture having a low profile, readily accessible for repair and bulb replacement and aerodynamically shaped to help reduce wind damage. Desirably, such a light fixture could provide a broad spectrum of illumination over a flat surface so that, when used in combination with similar fixtures, a large billboard surface could be illuminated in a relatively uniform manner while substantially reducing light pollution.
Ideally, such a light fixture would be low in cost to manufacture, being constructed of readily available materials.